Charon's surface is known to consist primarily of water
ice, so the similar
colors of P1 and P2 suggests that these moons have water ice surfaces, too.

The finding
supports the theory that all three of Pluto's
moons were formed from a single giant
impact that took place about 4.6 billion years ago. Recent observations
about the orbital
motions of Pluto's recently discovered moons, P1
and P2, also support this theory.

"Everything
now makes even more sense," said Alan Stern of the Southwest Research
Institute (SwRI). "If all three satellites
presumably formed from the same material lofted into orbit around Pluto from a
giant impact, you might well expect the surfaces of all three satellites to
have similar colors."

Stern,
principal investigator for NASA's New
Horizons mission currently headed toward Pluto, and colleague Hal Weaver of
Johns Hopkins University's Applied Physics Laboratory, led
the research team that identified the color of the distant planet's
new found moons using the Hubble Space Telescope. The finding was announced
earlier this month.

The team
found that P1 and P2 have essentially the same color as Charon's
surface. The surfaces of all three moons reflect sunlight with equal efficiency
at all wavelengths; this property also applies to Earth's moon.

Pluto's
surface, in contrast, has a reddish hue, which is believed to be the result
of interactions between sunlight and nitrogen and methane surface ices.

The finding
was detailed in a recent International Astronomical Union Circular (IAUC), a
scientific newsletter which details recent astronomical discoveries.